1. Field of the Invention
The present invention relates to a part for an ion implantation device which is used in the ion implantation device in which an impurity element (a doping element) is incorporated into a wafer.
2. Description of the Related Art
The manufacturing of a semiconductor device includes an implantation process in which a doping element is injected in a silicon wafer. There are mainly two methods used in the implantation process: a method of diffusing vapor phase heat in a diffusion furnace at high temperature; and an ion implantation method in which a doping element is accelerated and implantated in the wafer surface. Since the amount of dope and the like can be accurately controlled, the ion implantation method has become mainstream in recent years.
As shown in FIG. 1, an ion implantation device 10 used in ion implantation methods includes an ion generating portion 12 which generates ions from gases such as BF.sub.3, PH.sub.3, AsH.sub.3, or the like; a gas supplying portion (not shown) which supplies gas to the ion generating portion 12; a withdrawing electrode 14 which withdraws the generated ions from the ion generating portion 12 and forms an ion beam; a mass analyzing portion 16 whose planar configuration is substantially L-shaped, and which applies a predetermined magnetic field to the ion beam and extracts only the desired type of ion as the rate of curvature of the orbit, which curvature is caused by the applied magnetic field, depends on the type of ion contained in the ion beam; a beam line portion 20 which is continuous with the mass analyzing portion 16 and is disposed so as to be substantially perpendicular to the orbit of the ion beam formed by the withdrawing electrode 14; an aperture 22 which is disposed on the opposite side of the beam line portion 20 with respect to the mass analyzing portion 16 and sets the radius of the ion beam to a predetermined radius; an acceleration portion 24 which is continuous with the beam line portion 20 and accelerates the energy of the ions to predetermined levels; and an implanting portion 28 which injects the accelerated ions into a substrate 26.
Various parts are included in the ion implantation device 10. The parts must satisfy the following characteristics: (1) heat resistance and durability against ions or plasma are good, (2) no harm is done to the semiconductor device serving as a product (low contamination), and (3) even if ions collide with the ion implantation device, atoms or molecules harmful to semiconductor devices are not ejected above permissible levels (low sputtering). In order to satisfy these characteristics, carbon materials such as graphite or vitric carbon are used for the parts.
Recently, carbon materials with considerably high purity have become available, but the ion resistance of the carbon material is not very high.
As a result, ceramic materials with heat resistance comparable to that of carbon materials and having high level hardness and excellent ion resistance are desirable. Above all, silicon carbide is the most desirable since the elements thereof are harmless to semiconductor devices serving as products.
However, because it is difficult to sinter silicon carbide, a small amount of boron carbide, alumina, or the like is generally added to the silicon carbide as an additive for facilitating the sintering. Since these additives become impurities, a conventional silicon carbide is inappropriate as a material of the aforementioned parts for an ion implantation device.
Accordingly, a silicon carbide sintering method and a sintered body which does not use the aforementioned harmful additive are desired. For example, i) a method of manufacturing a sintered body with fine powder formed through vapor phase epitaxy employing gas or a solution including silicon and carbon as a material and by using the formed powder as a material; and ii) a method of manufacturing directly a plate-shaped molded body (sintered body) through vapor phase epitaxy employing gas or a solution including silicon and carbon as a material are proposed.
However, in these methods, there are drawbacks in that the productivity is very poor and the cost is high. Further, the above-described Method i) has a drawback in that the powder is too fine and particles are easily generated even after the powder is sintered. Method ii) has a drawback in that it is difficult to manufacture a thick molded body.